WI-38 cells represent normal diploid human fibroblasts and have been well characterized. A transformed WI-38 cell line, 2 RA, is available. The normal cells will enter a resting stage of the cell cycle, Go, while the transformed cells will not. These abnormal cell lines represent good models for the study of differences between normal and transformed cells. The goal of this proposal is to ascertain whether the transformation process results in abnormal aspects of DNA synthesis. Parental DNA will be purified from transformed cells in various phases of the cell cycle and examined for structural alterations. Newly-synthesized DNA will also be examined for structural alterations. The kinetics and pattern of interconversion of nascent DNA intermediates, from the earliest to chromosomal DNA, will be determined. The rate of DNA synthesis and rate of DNA chain elongation for various parts of the S-phase of the cell cycle will be determined. All findings will be compared with results from similar studies on normal cells (WI-38) already performed in this laboratory.